Self generating and self marking multiplication, addition and subtraction grid (with timer)

A macro based excel sheet that will generate unique multiplication grids and self marks them. Grids can then be saved and exported as a PDF or simply printed.

***If you encounter any problems when opening, please let me know so I can fix them***

There is also an addition grid and subtraction grid (top row minus column). The same unique generation and self marking functions apply.

A second option could be to print these grids for use in class instead of using the self marking format.

Instructions for use:
Grid should always maximise on start.

To generate a multiplication grid, click the "Multiplication Grid" button. Likewise for addition or subtraction. If this button is pressed at any point, it will clear all current inputs and generate a new grid.

You can only input answers into the grid when the timer is running. It will keep count in the background, and display the total time to complete both grids when finished. You cannot stop the timer, save or print midway through a grid.
(Press the reset button to stop the timer, but this will also clear the grid!)

Save - this button will save the work as a PDF file. You can save blank ones for future use, but once the timer starts the grids can only be saved when fully completed.

Print - Asks the user to select a printer and will print the current grids but omits the buttons. Same rules as above - can print blank, can't print midway.

If there are any issues, or requests, please comment and let me know. I am a fairly amateur VBA user but I have tried my best to foresee any errors that may arise.

An excel file (Macro based, and possibly requires Windows 8 or later).